1. Field of the Invention
This invention relates to a method of cementing an oil or gas well using construction grade cement.
2. Background Information
Cements are divided into various classes depending upon their chemical and physical properties and their application. For instance, the American Society for Testing and Materials (ASTM) divides cement into various types. The ASTM classes of cement range from Type I through Type V. In the oil and gas well construction industry, the American Petroleum Institute (API) has set standards for different classes of cement, similar to those established by the ASTM. The API has divided cements for use in oil and gas wells into eight different classes, classes A through H. Because stricter requirements are necessary for some cements to ensure proper performance of the cement and the cement slurry, it is necessary to have these different classes. Cement and cement slurries which are pumped downhole within oil and gas wells are subjected to various types of energy. This energy is mainly kinetic and thermodynamic energy having different intensities and duration levels which affect the cement's hydration rate, morphology and slurry properties.
Construction grade cement is commonly available from a variety of manufacturers and is very inexpensive compared to the higher grades of cement used in cementing oil and gas wells. While construction grade cement may be suitable for a large number of surface applications, they seldom meet the requirements established by the API for parameters such as thickening time, free water, compressive strength and chemical makeup. The composition of the construction grade cements also varies from manufacturer to manufacturer making it hard to predict the physical properties of the resulting cement and cement slurry. Thus, construction grade cements are seldom, if ever, used in downhole applications. This is particularly true when cementing intermediate and production casings of oil and gas wells.
Because construction grade cements are readily available and quite inexpensive, it would be advantageous to be able convert or utilize construction grade cement in oil and gas wells, particularly when cementing intermediate and production casings.